But jump ahead a half-century to Pero Fernandes's map of 1545 -- and the planet is utterly transformed. A huge wave of exploration has brought the world into focus for the first time: Africa has taken on its distinctive shape, India is no longer an insignificant bump, the Pacific is there in all its vastness, and the Americas have appeared. Guesswork has given way to knowledge: A new world, with all its complexities and possibilities, has suddenly come into being.

... "the objects reflect disturbing ambiguity more often than cheerful multi-culturalism" ...

The two maps -- works of art in themselves -- are part of a massive new exhibit opening today at the Sackler Gallery. Called "Encompassing the Globe: Portugal and the World in the 16th and 17th Centuries," it's a broad, impressionistic look at the trading empire built by the Portuguese that stretched from Brazil to Africa to Japan -- an empire that brought an explosion of knowledge to the Renaissance, fueled European expansionism and launched (for good or ill) the integration of the modern world.

"It's hard for us to imagine how transformatory this period was," says Julian Raby, the director of the Smithsonian's Sackler and Freer galleries. "It's the first moment of globalization -- information about the variety of the world, in terms of its peoples and cultures, was just pouring in. And part of what we want to get across is that sense of wonder at the complexities and textures of the world."

With roughly 275 objects on display, that shouldn't be a problem. "Encompassing" is the largest single exhibit in the Sackler's 20-year history -- taking up all its exhibition space and spilling over into the adjacent Museum of African Art -- and undoubtedly the most diverse. There are African ostrich eggs in ornate gold mounts, intricately carved crucifixes from Sri Lanka, a life-size oil painting of a Brazilian cannibal, Chinese astrolabes, Indonesian puppets, a Japanese shield covered in the skin of a ray, and a bewildering array of other wonders.

Yet, despite its global scope and almost runaway eclecticism, the exhibit is more than just souvenirs from a sprawling empire. "We looked for works of real aesthetic significance," says Jay Levenson, the show's guest curator, who scoured more than a hundred collections around the world to assemble the exhibit. "Works that told the story of the voyages, but that also documented the interchange among cultures."

For all that it changed the world, Portugal's empire remains largely unknown in America, overshadowed by the Spanish voyages to the New World. But the explorations that started in 1419 under Prince Henry the Navigator (particularly Vasco da Gama's opening up of a sea route around Africa in 1498) were at least as important, laying the foundations of global maritime trade and establishing an empire that endured until modern times; the last outpost, Macau, was only handed over to China in 1999.

But it was an unusual empire, designed not for conquest but for trade and, to a lesser degree, for spreading Christianity. The early voyages down the coast of Africa were aimed at breaking the Islamic world's monopoly on trade with the East, and forging an alliance with the mythical Prester John, a Christian king thought to rule somewhere in Africa. Using small, lightly armed flotillas of ships, the Portuguese established trading relationships rather than colonies. And as they ventured ever more deeply into Asia, they found themselves interacting not with the primitive world they'd expected but with complex, deeply embedded cultures and flourishing economies.

"It's much more about relationships between equals," says Levenson. "It's about trade and the exchange of knowledge."

Empire-building of any kind is rarely a pretty business, though. And in fact, the Portuguese weren't out to foster greater understanding among the peoples of the world -- they were after control of the trading routes, and they were ruthless. Slave trading was rampant, uncooperative ports were bombarded, and piracy abounded. In one memorable episode, da Gama himself locked nearly 400 Muslims onto a ship and burned them alive -- including women and children.

"Many of the artworks were gained at a very high price," says Raby, "whether it was the death of indigenous peoples, through the diseases that were brought by Europeans, or by often quite violent encounters."

And in a sense, that's part of what makes "Encompassing" such a fascinating exhibit: It puts objects on display that reflect disturbing ambiguity more often than cheerful multiculturalism. Each of the encounters was different, but the artworks that resulted rarely show a free hybridization of cultures; many, in fact, almost seethe with tension.

Take, for example, a remarkable ivory saltcellar from 16th-century Nigeria. Probably made as a trade item for European collectors, it's a beautiful, intricately carved piece that shows a group of Portuguese sailors (who would have been involved in the slave trade) supporting a ship. The sailors' faces are carved almost like African masks, and the ship's captain holds an African spear in one hand. The effect is charming -- until you notice the small, wide-eyed face peering out from inside the ship, and the objet d'art suddenly takes on a disturbing edge.

The complex relationships between the Portuguese and the cultures they encountered becomes even more apparent in the art from Asia, or "Estado da India," as the network of Portuguese enclaves throughout the region came to be known. Most of the outposts were small trading centers, designed to manage the lucrative spice trade. But Lisbon also held substantial territories, including Bombay and Goa, and where the Portuguese held physical control, they held cultural and religious dominance as well -- driven in part by Jesuit missionaries seeking converts.

"Goa in the 16th century was a territory of some hundreds of square miles, with maybe a million people," says Sanjay Subrahmanyam, a professor at UCLA and author of The Portuguese Empire in Asia, 1500-1700. "And there you're talking about forcible conversion, the destruction of Hindu temples, the elimination of the Muslim population."

It wasn't all conversion by force, but even so, the degree of Christian influence is striking in the exhibit's Indian artworks. Many are stunning; a 17th-century communion table from Gujarat mixes European and Indian styles with effortless grace, and an elaborate ivory carving with Christ as a lute-strumming shepherd draws deeply on Indian sculptural traditions; at first glance it could be taken for a work of Buddhist art.

But a far more revealing work may be the ivory plaque that depicts the infant Jesus sailing one of the Portuguese trading ships. It's called "Young Christ as the Mariner on the Ship of Salvation," but the obvious ingratiation goes deeper than the title. The masterful Sri Lankan artist who carved it purged all traces of his culture from the work; it looks like something out of an Italian Renaissance workshop. As art, it's lovely. As an exercise in cultural self-abnegation, it's somewhat chilling.

Other imperial tensions simmer throughout the exhibit, in remarkably different ways. In China, the Portuguese impact was so weak as to be almost undetectable; Beijing adopted Lisbon's superior astronomical knowledge but kept the rest at a studied distance.

In Japan, however, things turned disastrous. There the Portuguese initially met with success, winning some 150,000 converts to Christianity. But it quickly became their undoing; the ruling shoguns outlawed the religion, expelling missionaries and forcing suspected Japanese Christians to stamp their feet on bronze plaques bearing the face of Jesus -- known as fumi-e -- to prove their indifference.

It was only in Brazil, in fact (discovered virtually by accident by Pedro Alvares Cabral in 1500), that the Portuguese were able to build a large-scale colony as opposed to smaller outposts. Easily overcoming the indigenous Tupi people, Lisbon eventually set up huge sugar plantations, bringing hundreds of thousands of slaves over from Africa and, over the next few centuries, becoming the leader of the transatlantic slave trade.

Although that disturbing side of the empire is touched on only lightly, several paintings of Africans and Tupi by the 17th-century Dutch painter Albert Eckhout offer a gripping insight. Scaled to heroic size, the paintings were commissioned as "promotional literature" to encourage investment in the plantations, says the Sackler's Raby -- designed to show Europeans how native peoples benefited from the civilizing aspects of colonization.

And for all its multicultural aspirations, it's hard not to hear faint echoes of a similar spin in "Encompassing the Globe." Ever since its discoveries were celebrated by Luís Vaz de Camoes in his epic 16th-century poem "The Lusiads," Portugal's empire has been at the heart of its national identity, the rough edges softened and the myths massaged. Financed largely by Portugal's Ministry of Culture and dozens of Portuguese banks and corporations, "Encompassing" could be read as a paean to Portuguese imperialism, sheltering from hard questions in its own sheer vastness. But in the end, the artworks reveal a deeper and infinitely more satisfying story -- the tense, difficult and sometimes brutal birth of the modern world.